The present invention generally relates to dairy farm machine milking and particularly to a method and an apparatus for detecting liner slips during machine milking, i.e. when the liner slips on the teat of an animal due to air leaking past the teat and the liner.
In modern dairy farm industry there are continuous research and development activities in order to improve the efficiency of milking machines, which, inter alia, involves increased milk yield, reduced milking time, while still maintaining good udder health.
One of the parameters in this respect is the presence of liner slips. These slips, that occasionally appear, may affect, i.e. increase the occurrence of udder infections, which results in a deteriorated milk quality. Besides, many liner slips produce an irritating noise, and if the slip is large the milking equipment may even fall off the animal. Thus, milking equipment should be designed to introduce as few liner slips as possible, and preferably no liner slips at all. Therefore, the number of liner slips is monitored during development and testing of different equipment.
Manual counting of liner slips by virtue of listening for the noise that they cause have been performed at test farms, but such a method is time consuming, labor intensive, costly, and to a certain degree unreliable as one has to rely on the human perception.
Attempts have been made to solve the problem of the lack of a reliable liner slip measuring system using some different approaches.
Measuring increased air flow through the system as a measure of the degree of liner slip is disclosed by G. A. Mein et al. in Air leakage past the teat and teatcup liner during milking, Aus. J. Dairy Tech., March 1973 and by E. J. O""Callaghan in Measurement of liner slips, milking time and milk yield, J. Dairy Sci. 79:390, 1995. A liner slip was defined by O""Callaghan as an air inlet larger than 35 l/min. Drawbacks associated with this method includes, inter alia, time-demanding re-calibration during the measurement and the requirement of voluminous equipment.
Measuring the vacuum drop in the claw was proposed by S. B. Spencer and C. Volz in Measuring milking machine liner slips, J. Dairy Sci. 73:1000, 1989. They suggested a vacuum drop of 8 kPa in less than 0.25 seconds as a criterion for a liner slip. Subsequent to a detected liner slip, the detector was blocked during five seconds in order not to detect subsequent fluctuations, that might occur, as a further liner slip. This approach may, however, not always provide adequate protection from mechanical damage of the measuring equipment; for instance external electric connection cables to the claw will be needed, which further infers that it may not operate satisfactorily in the long run. The approach also puts restrictions on the size of the sensor to be employed.
Accordingly, it is an object of the present invention to provide a method for detecting liner slips in a milking machine which involves, for each milking unit, a clawpiece and a cluster of teat cups connected to the clawpiece, wherein each teat cup has a shell body and an internal flexible liner, said liner comprising a mouthpiece and a body part, whereby the liner extends through the bottom of the shell body as a short milk tube and is connected to the clawpiece and further, by way of a long milk tube, to a source of steady vacuum, while the annular space, between the teat cup shell body and the teat cup liner, is connected to the clawpiece by a pulse tube and further to a source of pulsating vacuum, which avoids at least some of the problems discussed above.
It is in this respect a particular object of the invention to provide such a method that is effective, accurate, reliable, easy to install and maintain, and particularly of a low cost.
It is yet a further object of the invention to provide the method in such a way that it is easily reconfigurable to meet changing demands.
These objects among others are, according to one aspect of the invention, fulfilled by a method wherein a milking machine system is provided, the milking machine system having at least one milking unit. Each of the milking units include a clawpiece and a cluster of teat cups connected to the clawpiece, each of the teat cups having a shell body and an internal flexible liner. The liner includes a mouthpiece and a body part whereby the liner extends through the bottom of the shell body as a short milk tube and is connected to a source of steady vacuum by way of a long milk tube. An annular space is located between the teat cup shell body and the teat cup liner, the annular space being connected to the clawpiece by a pulse tube and further to a source of pulsating vacuum. The method includes the steps of sensing the pressure in the system downstream of the long milk tube and the step of detecting a liner slip in dependence of a predetermined change in the sensed pressure.
A further object of the present invention is to provide an apparatus for performing the method according to the first aspect of the invention.
In this respect, it is yet a further object of the invention to be integratable in existing machine milking systems.
Consequently, there is according to a second aspect of the present invention provided an apparatus for use in a milking machine having at least one milking unit. Each of the milking units include a clawpiece and a cluster of teat cups connected to the clawpiece, each of the teat cups having a shell body and an internal flexible liner. The liner includes a mouthpiece and a body part whereby the liner extends through the bottom of the shell body as a short milk tube and is connected to a source of steady vacuum by way of a long milk tube. An annular space is located between the teat cup shell body and the teat cup liner, the annular space being connected to the clawpiece by a pulse tube and further to a source of pulsating vacuum. The apparatus includes a pressure sensor located downstream of the long milk tube for continuously or discontinuously sensing the pressure in the system downstream of the long milk tube and a detector connected to the sensor arranged for detecting a liner slip in dependence of a predetermined changed in the sensed pressure.
Yet a further object of the present invention is to provide a method for detecting liner slips in a milking machine system which involves, for each milking unit, teat cups, each having a shell body and an internal flexible liner, said internal flexible liner comprising a mouthpiece and a body part, wherein each liner extends through the bottom of the respective shell body and is connected, by way of a respective long milk tube, to a source of steady vacuum, while the respective annular space, between the shell body and the liner, is connected to a source of pulsating vacuum, which exhibits the above said characteristics.
Accordingly, there is according to a third aspect of the present invention provided a method for detecting liner slips in a milking machine system having at least one milking unit, each of the milking units including a plurality of teat cups and each of the teat cups having a shell body and an internal flexible liner. The internal flexible liner includes a mouthpiece and a body part, wherein each liner extends through the bottom of the respective shell body and is connected, by way of a respective long milk tube, to a source of steady vacuum. A respective annular space, located between the shell body and the liner is connected to a source of pulsating vacuum. The method of this third aspect includes the steps of sensing the pressure in the system downstream of the long milk tubes, and detecting a liner slip in dependence of a predetermined change in the sensed pressure.
Finally, an object of the invention is to provide an apparatus for performing the method according to the third aspect of the invention and hence, an apparatus is provided for detecting liner slips in a milking machine system having at least one milking unit. Each milking unit has a plurality of teat cups, each having a shell body and an internal flexible liner, the internal flexible liner including a mouthpiece and a body part. Each liner extends through the bottom of the respective shell body and is connected, by way of a respective long milk tube, to a source of steady vacuum. An annular space is located between the teat cup shell body and the teat cup liner and is connected to a source of pulsating vacuum. The apparatus includes a pressure sensor located downstream of the long milk tubes for continuously or discontinuously sensing the pressure in the system downstream of the long milk tubes, and a detecting means connected to said sensor arranged for detecting a liner slip in dependence of a predetermined change in the sensed pressure.
An advantage of the present invention is that while its sensor is implemented downstream of the long milk tube(s), it is protected from mechanical stress and no electric connections or the like is necessitated upstream of this point, which provides a reliable operation of the same.